31720721497 has 2 divisors, whose sum is σ = 31720721498. Its totient is φ = 31720721496.

The previous prime is 31720721477. The next prime is 31720721509. The reversal of 31720721497 is 79412702713.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17831863296 + 13888858201 = 133536^2 + 117851^2 .

It is a cyclic number.

It is not a de Polignac number, because 31720721497 - 2¹¹ = 31720719449 is a prime.

It is not a weakly prime, because it can be changed into another prime (31720721477) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15860360748 + 15860360749.

It is an arithmetic number, because the mean of its divisors is an integer number (15860360749).

Almost surely, 2^31720721497 is an apocalyptic number.

It is an amenable number.

31720721497 is a deficient number, since it is larger than the sum of its proper divisors (1).

31720721497 is an equidigital number, since it uses as much as digits as its factorization.

31720721497 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 148176, while the sum is 43.

The spelling of 31720721497 in words is "thirty-one billion, seven hundred twenty million, seven hundred twenty-one thousand, four hundred ninety-seven".